While the ad mentions birth control and gay marriage, Steyer is supporting Democratic incumbent Sen. Mark Udall and other embattled Democrats who support his environmental agenda. He’s vowed to spend up to $50 million of his own money supporting his favored candidates, matching contributions of others.

Tuesday’s ad, paid for by Steyer’s NextGen Climate Action Committee, features a house in which the occupants close the windows and draw the blinds in an effort to “keep Cory out.” While the spot opens with an attack on Gardner’s skepticism about the causes of climate change, it quickly ticks off a list of other issues in which he differs with Udall.

“He thinks he knows better than the scientists, NASA and the U.S. military on climate change and thinks government should decide who can and cannot marry,” says a female narrator.

“He led an eight year crusade that would outlaw birth control and make abortion a felony crime,” she continues.

Udall has repeatedly hit Gardner on the women’s health issue, highlighting his past support of personhood legislation that Gardner only disavowed earlier this year.

While Steyer told a renewable energy summit in Aspen last week that the focus of his campaign will be more on getting out the vote than on wooing swing voters, a NexGen spokesperson made clear that Tuesday’s ad won’t be the last of its kind.

“As an elected official, Gardner has relentlessly tried to impose his extreme views to reduce or stop the funding of science research on climate change and to interfere on women’s health issues to the point where he would have made abortion a felony,” spokesperson Abby Leeper told Denver’s Fox 31.

“And now he wants to ‘shake up the Senate’ with his harmful Gardner-knows-best attitude. Congressman Gardner’s voting record is outside the mainstream in Colorado, and NextGen Climate will continue to point that out through the election.”

On Wednesday, the National Republican Senatorial Committee released an eight-minute biographical film about Gardner in which he touts the economic benefits of oil and gas development. The spot doesn’t mention Udall, but instead focuses on Gardner’s background and legislative style.

Gardner and Udall are in a dead heat. The Colorado Senate race is expected to be one of the most expensive in the country.

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